The present invention relates to twist ties in general. More specifically to a substantially polymeric tie that is comprised of a thermoplastic monofilament that is bonded to the center portion of a flat ribbon like thermoplastic substrate.
Previously, many types of twist ties have been used in endeavoring to provide an effective means for closing or tying articles such as bags, fastening plants to stakes, securing bundled electric cable and other restraining tasks. These ties have included strings, wires, adhesive tape, and ribbon sandwiched onto a metallic wire. The most common type of tie presently in use today is a pair of ribbons having a wire bonded in between with the ribbon fabricated of either plastic, paper or both. Attempts to eliminate the wire have resulted in unitary extrusions having a bulb-shaped central portion even to the extent that a core of rubber, or the like, is simultaneously extruded in the center. Other embodiments of tie material include foil strips or a number of strands of wire in parallel alignment, further attempts have been made to make the tie completely of thermoplastic material that acts like wire by orienting the plastic with heat and stretching also by adding fillers to the formulation to add stiffness and malleability.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however the following U.S. patents are considered related:
Feltman in U.S. Pat. No. 5,607,748 teaches a wireless polymeric twist tie that includes a wing portion and one or more leaf portions. The twist tie is formed from an extruded non-metallic polymeric composition in a single indivisible form. The twist tie is fabricated of a material having both a tensile and yield strength of greater than 9,000 pounds per square inch.
U.S. Pat. No. 5,342,687 issued to Iwai et al. is for a non-metallic coreless twist tie formed by melting polymeric material, extruding the material in an elongated form, cooling then drawing the material at a rate of at least 2.5 times. The material may include 3 to 50 parts of glass beads and is formed from a resin having 10 to 60% crystallization at a temperature of 100 to 250 degrees centigrade.
U.S. Pat. No. 5,154,964 also of Iwai et al. discloses a similar twist tie, as above, with the glass beads added to the polymeric material having a particle size of less than 60 microns.
Stolk et al. in U.S. Pat. No. 4,797,313 teaches a non metallic polymeric ribbon deformed under tensile stress at 25 degrees centigrade and a strain rate between 0.1 and 0.5 inches per inch per minute. Optional materials are also employed in various polymers.
U.S. Pat. No. 4,391,063 issued to Gill, III discloses a sealing device for a balloon utilizing a thin strip of foil attached to a flexible retaining line. The strip is coated on one side with a pressure sensitive adhesive and folded to form the sealing device and also to attach to the line.
U.S. Pat. No. 3,409,948 issued to Goodwin is for a twist tie that employs a plastic ribbon bonded to a paper ribbon in a face-to-face relationship. The plastic ribbon includes a longitudinal channel and a metallic wire that is disposed within the channel between the ribbons and a cementitious coating is applied bonding the wire, paper and plastic ribbon together.
UK patent No. GB 2,060,469 issued to Ward is for the deformation of thermoplastic polymers by solid phase deformation and concomitant orientation of various polymers. The polymer may be filled with glass, asbestos, metal carbon, ceramic whiskers of silicon carbide or the like. The thermoplastic polymer is drawn through a die with tension insufficient to cause failure but progressively increasing the strain along with an elevated temperature of the die.
For background purposes and as indicative of the art to which the invention is related reference may be made to the remaining cited patents issued to Betner.
A primary object of the invention is to overcome the problems that are prevalent in today""s industry using a metallic wire sandwiched between two ribbons. In the food industry where their use is widespread, typically bread bags, and other polyethylene bags for various edible products, the ties are mechanically attached and have die cut sharp ends that may inadvertently puncture the bag itself exposing the product to the atmosphere or even piercing the users fingers or hands.
It has been a common practice in the food industry to automatically inspect many packages for the presence of metal, such as sliced foods, as cutting blades may leave traces of metal within or near the product. It may be clearly seen that this automatic procedure makes the use of a wire embedded tie extremely objectionable at best and may even eliminate the possibility of its use entirely.
It is apparent that hazards exist particularly with young children that could accidentally ingest the tie which contains a metal in a pliable form and has very sharp ends that could ultimately lead to internal body damage.
Also since a conventional tie utilizes metal in its composition the original product package employing this type of tie may not be heated in a microwave oven as high frequency radiation arcs when metal is present thus necessitating additional and unnecessary handling and preparation of the packaged product by the user.
Another disadvantage to the use of metal in the tie material is that where the ends of the wire that have been cut off or the plating has been worn off by repeated twisting this surface may introduce undesired oxidization or rust in the presence of moisture.
A further disadvantage of the conventional configuration of the paper and wire tie is that over continued usage the paper covering the wire often twists off and falls away leaving the wire bare or partially stripped making it hard to handle and manipulate for further reuse.
There have been numerous attempts to produce a unitary non-metallic cordless thermoplastic twist tie that possesses the advantages of using a metal wire without all of the drawbacks, however, all of the known metal free ties have not as yet proven to be fully satisfactory and are not widely accepted in the industry at the present time.
An important object of the invention is to utilize a combination of thermoplastic materials with the core made of a substance that has the properties of metal wire, in that it is malleable and stays bent to a useable extent, and a ribbon that stretches out of the way without breaking and substantially reverts to its normal body shape when untwisted. This composite of dissimilar materials permits the core or filament to be twisted and retain this union with an attached substrate, forming the wings, expanding and following the filaments orientation without yielding.
Another object of the invention is that the twist tie is fabricated of two separate elements of dissimilar materials and processes bonded together permitting the best properties of each material or process to be selected without compromise. This composite of separate elements allows the ribbon to be chosen from a myriad of available sources using economies of number and a monofilament that is either presently obtainable or may be fabricated using a conventional yet customized procedure. The substrate or ribbon selected has the ability to spread the load around the bag or container to which it is closing and also to resist tearing when twisted. The monofilament replacing the wire has been selected for its dead fold properties and its ability to be easily twisted together and stay connected, also, its repeatability in this operation. Many plastic materials are rigid enough to be bent and retain a angular displacement, however, the thermoplastic must not be too stiff or brittle or it will not function properly as its ability to repeatedly duplicate twisting is of paramount importance. Both thermoplastic materials in use with this invention are compatible with each other permitting a homogeneous bonding together using conventional procedures.
Yet another object of the invention is the ease of manufacturer as the substrate may be purchased on the open market in the film configuration the proper width with no further modification necessary. The monofilament may also be purchased in a round rod form the proper diameter ready for orienting. Further the equipment necessary for orienting the monofilament, while special in some minor details, is readily available as well as the bonding apparatus all of which are well known in the art allowing the finished product to be competitively priced creating an advantage to the public.
These and other objects and advantages of the present invention will become apparent from the subsequent detailed description of the preferred embodiment and the appended claims taken in conjunction with the accompanying drawings.